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Common problem

Numerical control machine tool "size instability" 9 cause analysis


1. Accurate size of workpiece and poor surface finish
Cause of failure: tool tip is damaged, not sharp; The machine tool produces resonance, the placement is not smooth; The machine has a crawling phenomenon; The processing technology is not good.

Solution: tool wear or damage not sharp, then retool or select a better tool to re-use the knife; The machine tool produces resonance or placement instability, adjustment level, laying the foundation, stationary; Mechanical causes of crawling to slide guide rail wear, screw ball wear or loose, should pay attention to machine maintenance, after work should be cleaning the wire, and in a timely manner to add lubricant to reduce friction; Select the coolant suitable for workpiece processing, and choose the high spindle speed as far as possible in the case of other machining requirements.

2. The workpiece produces taper size head phenomenon
Cause of failure: the level of machine tool placement has not been adjusted well. In the long axis of turning, the contribution material is hard, the cutter is more deep, causing the knife phenomenon; The tail thimble is different from the spindle.

Solution: adjust the levelness of the machine tool with the horizontal instrument, lay down a solid foundation, and fix the machine tool to improve its toughness; Choose reasonable technology and proper cutting feed to avoid the knife. Adjust the tail seat.

3. The phase lamp of the driver is normal, and the workpiece size is small when it is processed
Reasons for the failure: the long running of the towing plate of the machine, causing wear of the rod and bearing; The repeated positioning precision of the tool holder is biased in the long-term use. Each time the dragboard can get back to the starting point accurately, but the workpiece size still changes. This kind of phenomenon is usually caused by the main shaft, the high-speed rotation of the main shaft causes the bearing to wear seriously, resulting in the change of the machining dimension. Metal processing WeChat, good content, worthy of attention.

Solution: use a percentage of the base of the tool holder and edit a fixed loop program through the system to check the repeat positioning accuracy of the dragboard, adjust the clearance of the screw rod, and replace the bearing; Check the repeat positioning accuracy of the tool holder with a dial, adjust the machine or replace the tool holder; After testing the workpiece with a percentage gauge, it is accurate to return to the starting point of the program. If it can, overhaul the main shaft and replace the bearing.

4. The size of the workpiece is a few millimeters away from the actual size, or a certain axis has changed greatly
Cause of failure: fast positioning speed is too fast, the driver and motor are not able to react; After the long friction loss, the mechanical drag plate screw and the bearing are too tight to die; The knife holder is too loose after changing the knife. The program error of the editor, the head, the tail did not echo or did not cancel the knife completion; The system has an error in the electronic gear ratio or the step Angle.

Solution: quickly locate the speed, adjust the speed of GO, cut the speed and speed of the drive, and make the drive and motor work normally at rated operating frequency; After the wear of the machine, the towing plate and the screw bearing are too tight to die, the repair must be recalibrated; The tool holder is too loose after changing the knife to check whether the blade is satisfied, check whether the inner turbine worm is worn, whether the gap is too large, or whether the installation is too loose. If the program is caused by the procedure, the program must be modified, according to the drawing requirements of the workpiece, the reasonable processing technology shall be selected and the correct procedures shall be prepared according to the instructions of the instructions. If the size deviation is too large, check whether the parameters of the system are reasonable, especially if the parameters such as the electronic gear and the Angle of the step are destroyed, and this phenomenon can be measured by using a percentage.

5. The processing arc effect is not ideal, the dimensions are not in place
Cause of failure: overlap of vibration frequency leads to resonance; Processing technology; The parameter setting is unreasonable, and the feed speed is too high, so that the arc process is lost. The loosening of the large clearance of the screw rod or the loss of the screw thread; Synchronous belt wear.

Solution: find the components that produce resonance, change their frequency, and avoid resonance; Considering the machining process of the workpiece material and the reasonable programming; For stepping motor, the machining rate F is not too large; Whether the machine tool is installed firmly, the place is stable, the dragboard is not worn, the gap is enlarged or the blade is loose. Replace the synchronous belt. Metal processing WeChat, good content, worthy of attention.

6. In batch production, the occasional workpiece is too poor
The cause of the problem: must carefully check the jig, and considering the operation method, the operator and the reliability of the clamping, caused by the clamping size change, must improve the tooling making workers try to avoid human negligence made misjudgment phenomenon; The numerical control system may be affected by the fluctuation of the external power supply or interfere with the impulse of the interference, which can be passed down to the driver to accept or reduce the phenomenon of the excess pulse driving motor.

Solution: grasp the rule, try to use some anti-jamming measures, such as: strong electric field disturbance of high voltage cables and weak current signal of the signal isolation, join the absorption capacity of anti-interference and a shielding wire isolation, in addition, check whether the ground wire connection is firm, grounding contact recently, all anti-interference measures should be taken to prevent the system disturbance.

7. There is a change in the machining process of the workpiece, and the other processes are accurate

The reason of the fault: whether the parameters of the program are reasonable and whether the programming format conforms to the specifications in the intended trajectory

Solution: when the thread segment is disorderly and the pitch is incorrect, the peripheral configuration (encoder) and the objective factors of the function are immediately associated with the thread.

8. Each process of the workpiece has a phenomenon of increasing or decreasing
Cause of failure: program error; Unreasonable system parameter setting; Improper configuration Settings; Mechanical transmission parts have periodic and periodic failures
Solution: check the instruction program USES path execution, according to the requirement of the specification can be judged with a dial indicator, dial indicator positioning in the process of the starting point for dragging plate after the program is back to the starting location, repeat again even if observed as a result, to master its law; Check whether the system parameters are properly set or considered to be altered; The relevant machine tools are configured to calculate whether the single calculation meets the requirements on the coupling parameters and whether the pulse equivalent is accurate. Check whether the transmission part of the machine is damaged, the gear coupling is uniform, check whether there are periodic, regular fault phenomena, if any, check its key part and give it out.

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